Electronic properties of polyoxometalates:: A DFT study of α/β-[XM12O40]n- relative stability (M = W, Mo and X a main group element)
Electronic properties of polyoxometalates:: A DFT study of α/β-[XM12O40]n- relative stability (M = W, Mo and X a main group element)
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DOI：
10.1021/ja010768z
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发表时间：
2001-10-03
影响因子：
15
通讯作者：
Poblet, JM
中科院分区：
文献类型：
--
作者：
López, X;Maestre, JM;Poblet, JM
Keggin杂多阴离子[XM 12 O 40]（n-）有各种异构体结构，α和β是最常见的。通常，cc结构似乎是最稳定的，但是在DFT水平上对X = P（V）、Si（IV）、Al（III）、As（V）、Ge（IV）和Ga（III）以及M = W（VI）和Mo（VI）进行的计算表明，这种稳定性取决于几个因素，特别是杂原子（X）的性质和簇的总电荷。在本文中，我们应用包合物模型的Keggin分子进行片段相互作用的研究，以阐明何时以及为什么传统的相对稳定性的各种异构体可以，反转。在该系列中，完全氧化的阴离子已经逆转了传统的稳定性趋势，它们是[AlW 12 O 40]（5-）和[GaW 12 O 40]（5-），两者都含有第三族杂原子，总电荷为-5。β-异构体总是比α-异构体更容易被还原。该实验观察表明，还原有利于β-异构体的稳定性，并且该研究的最重要结果之一是在大多数情况下在第二次还原后实现α/β转化。α-和β-异构体可以具有不同的性质，因为LUMO（一种与能量适配的d（xy）-金属轨道）的能量不同。
Keggin heteropolyanions [XM12O40](n-) have various isomeric structures, alpha and beta being the most common. Conventionally, the cc structure appears to be the most stable, but calculations carried out at the DFT level for X = P(V), Si(IV), Al(III), As(V), Ge(IV), and Ga(III) and M = W(VI) and Mo(VI) show that this stability depends on several factors, particularly on the nature of the heteroatom (X) and the total charge of the cluster. In this paper, we apply the clathrate model to the Keggin molecule to carry out a fragment-interaction study to elucidate when and why the traditional relative stability of various isomers can be, inverted. The fully oxidized anions that have inverted the traditional stability trend in this series are [AlW12O40](5-) and [GaW12O40](5-), both of which contain a third-group heteroatom and an overall charge of -5. beta -isomers are always more easily reduced than alpha -isomers. This experimental observation suggests that reduction favors the stability of beta -isomers and one of the most important results of this study is that the alpha/beta inversion is achieved in most cases after the second reduction. The alpha- and beta -isomers may have different properties because the energy of the LUMO, a symmetry-adapted d(xy)-metal orbital, is different.